Echinococcus multilocularis and Other Intestinal Parasites of the Red Fox (Vulpes vulpes) from the Pomerania Region, Northern Poland.

The aim of the study was to determine the species composition of the intestinal parasite fauna of foxes from the Pomerania region, with a particular emphasis on helminth species considered dangerous to humans, and to determine their prevalence and intensity of infection. In total, 165 digestive systems from foxes inhabiting the Pomeranian region were examined. The prevalence of intestinal parasites among the studied foxes was 61.8%. Our findings confirm that foxes in Pomerania carry various parasites, some of which pose a direct threat to human health. As such, constant monitoring of their infestation is essential. Particular attention should be paid to parasite species with potential for transmission to humans, such as Echinococcus multilocularis, Alaria alata and Toxocara canis, whose respective prevalence was found to be 10.9%, 17.6% and 28.5%.

Diphyllobothrium sp. and Other Parasites of Migrating and Rare Fish Species in the Southern Baltic Sea and Coastal Waters, Poland.

The present study is the first to analyse the parasite fauna of sole Solea solea, dab Limanda limanda, hake Merluccius merluccius, whiting Merlangius merlangus, and plaice Pleuronectes platessa in the Pomeranian Bay, as well as saithe Pollachius virens from the Szczecin Lagoon (Poland). The aim of this study was to determine the occurrence of parasites in migrating and rare fish in the Pomeranian Bay and the Szczecin Lagoon and to determine the composition of the diet of these fish. The fish for analysis were obtained in the years 2010-2019. The typical marine nematode Capillaria (Procapillaria) gracilis, rarely recorded in Poland, was found, in addition to the following parasites: Ichthyophonus hoferi, Trichodina jadranica, Diphyllobothrium sp., Dichelyne (Cucullanellus) minutus, Raphidascaris acus, Anisakis simplex, Contracaecum osculatum, Hysterothylacium aduncum, Pseudoterranova decipiens, and Echinorhynchus gadi. Because the fish species analysed in the study are not typically present in the Baltic (with the exception of plaice), and because we do not know how long they feed while they are in the Baltic, we cannot be certain which parasites they acquired in the water bodies analysed in the study and which were introduced during the migration of fish. Although these fish are outside of their normal geographic range (except for plaice), in the new environment, there were enough suitable intermediate hosts for the parasites of these fish to complete their life cycle and survive.

New molecular data help clarify the taxonomy of central European avian dicrocoeliidae Looss, 1899 (Trematoda: Plagiorchiida).

Avian Dicrocoeliidae are difficult to identify, even in their adult stages. Molecular analyses have been conducted for only a few species, complicating the accurate identification of juvenile stages. The taxonomy of the family is unresolved, and the status of many dicrocoeliid species is uncertain. Sequences of nuclear and mitochondrial DNA loci of Central European avian Dicrocoeliidae were generated and analyzed. These included representatives of the genera Lyperosomum, Platynosomum, Stromitrema, Brachylecithum, Brachydistomum, and Lutztrema. All the sequences were obtained from morphologically identified adult specimens of dicrocoeliids isolated from avian hosts. Molecular support was obtained to validate Lyperosomum turdia, confirm the rejection of Lyperosomum dujardini and Lyperosomum alagesi, and resurrect Lyperosomum longicauda and Lyperosomum collurionis. The identity of European Platynosomum illiciens from avian hosts with American vouchers of the same species from avian and mammalian hosts was confirmed. Brachylecithum fringillae is not considered valid; the individuals that matched its diagnosis were subadult Brachydistomum ventricosum. Descriptions and comparative data for five new species are provided. These are Lyperosomum hirundinis sp. n., Lyperosomum tenori sp. n., Lyperosomum atricapillae sp. n., Stromitrema acrocephali sp. n., and Lutztrema atricapillae sp. n.. Based on the molecular data, suggestions are provided regarding the validity of dicrocoeliid species that parasitize Central European birds. Further research should address the polyphyletic status of Brachylecithum.

Helminth Community Structure of Tits Cyanistes caeruleus and Parus major (Paridae) during Their Autumn Migration on the Southern Baltic Coast.

The research problem undertaken in this study is to determine the scale of infection of Eurasian blue tit Cyanistes caeruleus and Great tit Parus major and the biological diversity of their internal parasites, helminths. The aim of the study is to gain new knowledge about the structure of the helminth communities of the Eurasian blue tit and Great tit on the southern coast of the Baltic Sea during autumn migration to their wintering grounds. Helminths of tits were collected in 2008-2012 on the southern coast of the Baltic Sea in Poland. PAST v. 2.11 software was used for the calculations. Barcoding DNA was used to identify trematodes initially classified based on morphological characters to the genera Leucochloridium and Urogonimus. Cestodes Anonchotaenia globata were recorded for the first time in Poland. The Eurasian blue tit is a new host in Poland for three species of helminths: cestode Monosertum parinum and filarial nematodes, Cardiofilaria pavlovskyi, and Diplotriaena henryi. The Great tit is a new host in Poland for trematode Urogonimus macrostomus, cestode A. globata and M. parinum, and filarial nematode Diplotriaena obtusa. The nematode C. pavlovskyi was the species most frequently recorded in both host species. A high degree of similarity was found between the component communities and infracommunities of helminths in Eurasian blue tit and Great tit. The new information provided in this study has increased our knowledge of the transmission of helminths in Central Europe.

Infection of Raccoon Dogs (Nyctereutes procyonoides) from Northern Poland with Gastrointestinal Parasites as a Potential Threat to Human Health.

The aim of the study was to determinate the prevalence and intensity of infection of raccoon dogs with internal parasites, with a particular emphasis on particular species of helminths known to be dangerous to humans. A total of 96 raccoon dogs were obtained from hunters from September 2018 to October 2021. The digestive tract was taken for examination. The parasitological examination was performed using the dissection methods. The extensity of infection with all internal parasites was 60.3%. The following parasites were found in the tested animals: Echinococcus multilocularis (in 10.42% of animals), Toxocara canis (18.75%), Alaria alata (25.0%), Taenia spp. (19.79%), Uncinaria stenocephala (27.08%), Mesocestoides spp. (54.17%) and Dipylidium caninum (6.25%). The highest mean intensity of infection was demonstrated by A. alata and E. multilocularis then by Mesocestoides spp. This study showed that the raccoon dog from northern Poland is a reservoir host of zoonotic pathogens, such as E. multilocularis, Toxocara canis and Alaria alata. Although the role of the racoon dog as a final host of the life cycle of E. multilocularis is considered of less importance than that of the red fox, this species may increase the risk of echinococcosis in humans, mainly due to its growing population in northern Poland.

Intestinal Helminth Communities of Grey Partridge Perdix perdix and Common Pheasant Phasianus colchicus in Poland.

The aim of this study was to describe the morphology and means of identification of helminths in native partridges (65) and introduced pheasants (32) in Poland and to determine the level of intestinal infection of these birds by helminths using parasitological and ecological indices. The birds were acquired during the hunting season in the years 2015-2017. Nematodes, Capillaria phasianina, cestodes, Railietina friedbergeri, and one trematode, Brachylaima sp. were recorded for the first time in partridges in Poland. Our findings indicate that parasites are more prevalent in pheasants (prevalence 70.4%) than in partridges (prevalence 50.0%). The component community and infracommunity of parasites of partridges are more diverse (Simpson's diversity index: 0.63 and mean Brillouin diversity index: 0.10 ± 0.17) and less dominated by a single parasite species (Capillaria sp., Berger-Parker dominance index: 0.53) than the pheasant parasite community (Simpson's diversity index: 0.07, mean Brillouin diversity index: 0.005 ± 0.02, dominant species Heterakis gallinarum, Berger-Parker dominance index: 0.96). There were statistically significant differences between partridges and pheasants in the Brillouin diversity index and in the prevalence of Heterakis gallinarum (55.6% in pheasants vs. 19.0 in partridges). There were significant differences between wild and farmed partridges in the prevalence of infection by Capillaria sp. (4.3% vs. 37.5%) and H. gallinarum (39.1 vs. 6.2%). In conclusion, the pheasant was shown to be a reservoir, carrier, and shedder of nematodes, which may increase the risk of infection in partridges.

Reproductive Potential of Stone Moroko (Pseudorasbora parva, Temminck et Schlegel, 1846) (Teleostei: Cypriniformes: Gobionidae) Inhabiting Central Europe.

Similar to other invasive species, stone moroko is extending its global distribution. The present study aimed to assess the reproductive potential of stone moroko fish in a new habitat in Poland based on analysing the sexual cycle and fecundity. Fish morphometric data, age, and gonadal structures were analysed. Fish age ranged from 0+ to 5+ years. Most females and males (93% and 60%, respectively) had reached sexual maturity in the first year of their life, with the smallest length of 25 mm and 28 mm, respectively. The mean, standard length of the body was 50 mm. The spawning season was spread over four months from late-April to mid-August. Females laid eggs in portions, and the absolute and relative fecundity was 1372 and 1691, respectively. Stone moroko males were ready to spawn for a longer time period than females. The present study shows greater reproductive potential of stone moroko population in the central Europe than the native population, suggesting its successful colonisation in the new habitat.

Microscopic and molecular detection of Deraiophoronema evansi (Lewis, 1882) in domestic Bactrian camels (Camelus bactrianus) of Mongolia.

Cameline filarosis is an important parasitic disease having an economic impact on the camel industry around the world. However, there has been no study on filarosis in Bactrian camels of Mongolia. Therefore, the aim of the present study was to detect and identify microfilariae of Deraiophoronema evansi (D. evansi) in Bactrian camels from three provinces, located in southern and southwestern Mongolia. Blood samples were obtained from 400 healthy two-humped camels of different ages and both sexes. All blood samples were analysed using a variety of diagnostic techniques. Microfilariae were detected in 30 Bactrian camels (7.5%) by the Knott technique, while 13 Bactrian camels (3.3%) tested positive in a direct smear test. D. evansi was detected in 18 Bactrian camels (4.5%) by PCR assay. Prevalence was shown to be high among Bactrian camels in the age group up to 5 years, while the lowest positive results were obtained for Bactrian camels in the 5-10-year age group and the over 10-year age group. To confirm the morphological identification, D. evansi-COI gene sequences were subjected to phylogenetic analyses. The D. evansi-COI gene sequences from Mongolian two-humped camels were identical to sequences from Iranian one-humped camels and were clustered together with these sequences in the phylogeny. This is the first report of molecular detection and identification of microfilariae of D. evansi in Bactrian camels of Mongolia.

GEOGRAPHIC AND ECOLOGIC ASPECTS OF THE COMMUNITY STRUCTURE OF TREMATODES OF MALLARDS (ANAS PLATYRHYNCHOS) IN NORTHERN POLAND AND THE CZECH REPUBLIC.

Trematode infestation of Mallards (Anas platyrhynchos) varies between northern Poland and the Czech Republic. We determined the trematode fauna of juvenile and adult Mallards from Poland in 2010-16 (n=79 Mallards) and from the Czech Republic in 1964-2001 (n=296). Infracommunity diversity of trematodes from juvenile Mallards, defined by the Brillouin index and mean number of species, was significantly greater in Poland than it was in the Czech Republic. There were more species and greater biodiversity in the trematode communities of Mallards from Poland, where the environment is more natural and less altered by human activity than it is in the Czech Republic. In the trematode community of juvenile Mallards, the Simpson's index of biodiversity was higher in the Czech Republic than it was in Poland. The Berger-Parker dominance index was comparable in both countries. In terms of prevalence, the structure of the trematode fauna was hierarchic, and trematode species had different positions in this hierarchy in the two countries. Statistically significant differences in the epidemiologic indices between infection of juvenile Mallards from Poland and the Czech Republic were noted for Bilharziella polonica, Echinostoma miyagawai, Echinostoma revolutum, Prosthogonimus cuneatus, Prosthogonimus ovatus, Notocotylus attenuatus, Echinoparyphium recurvatum, Australapatemon minor, Apatemon gracilis, Cyathocotyle prussica, Hypoderaeum conoideum, Metorchis xanthosomus, Psilochasmus oxyurus, and Cotylurus cornutus.

PCB residues in the tissues of sea ducks wintering on the south coast of the Baltic Sea, Poland.

The Baltic Sea is known to be severely polluted by a range of chemicals, one group of which being PCBs. Although the use and production of PCBs were limited or banned in many countries in the 1970s, their presence is still observed in the environment. The aim of this study was to evaluate PCBs concentration in four species of diving sea ducks, interspecies and tissues differences, and in the case of game species, comparison of the obtained results with maximal residue levels (MRLs) and tolerable weekly intake (TWI). The level of Σi-PCBs was noted in most examined samples (liver, muscle, fat tissue) at levels ranging between < LoD and 2315.45 ng/g lw. The dominant congener was PCB 153, followed by PCB 180 and 138. The mean dl-PCB-TEQ value in the muscles of the tested tufted ducks and common pochards was 0.31 and 0.71 pg-TEQ/g lw, respectively, which is 8-25 and 18-57% of the TEQ maximum limit (ML) value for farm animal muscles. The average decrease in i-ΣPCB concentration in the fat tissue of ducks wintering in the Baltic Sea southern coast was found to be 2.9-3.3%/year. The analysis of PCB residues indicates that the common pochard and tufted duck are not suitable for consumption due to high Σi-PCB concentrations. However, the regular consumption of muscle and liver of game birds does not result in an unacceptable intake of dl-PCBs, i.e., above the TWI value.

Central European Strigeidae Railliet, 1919 (Trematoda: Strigeidida): Molecular and comparative morphological analysis suggests the reclassification of Parastrigea robusta Szidat, 1928 into Strigea Abildgaard, 1790.

Strigeidae Railliet, 1919 are digenean parasites of birds and mammals that are characteristic by their cup-shaped forebody and bilobed holdfast organ. Despite that the family is taxonomically unsettled, particularly due to a very limited number of visible autapomorphic identification features, molecular phylogenetics have never been applied to analyze the relationships among European members of Strigeidae except for the genus Ichthyocotylurus. Here, we analyze the Strigeidae found during the examination of Czech birds performed from 1962 to 2017, and we provide comparative measurements and host spectra, including prevalence and intensity; we also provide and analyze sequences of four DNA loci of 12 of the Strigeidae species. We suggest the reclassification of Parastrigea robusta Szidat, 1928 as Strigea robusta (Szidat, 1928) Heneberg and Sitko, 2018 comb. n. The genera Strigea Abildgaard, 1790 and Parastrigea Szidat, 1928 appear paraphyletic, and morphological diagnostic features of genera within Strigeini Dubois, 1936 are invalid. The mute swan Cygnus olor hosts two Cotylurus spp., Cotylurus syrius Dubois, 1934 and a second species with molecular identification features shared in part with Cotylurus cornutus (Rudolphi, 1808) and Cotylurus gallinulae Lutz, 1928. New host records are provided for seven species. Analyses of non-European genera of the Strigeidae are needed to provide an updated key to Strigeini.

Taxonomic status of Syngamus nematodes parasitizing passeriform hosts from Central Europe: Morphological, morphometric and molecular identification.

The systematic position and validity of species within genus Syngamus have always been controversial. In this present work, we evaluated the taxonomic status and phylogenetic relationships between three species of Syngamus nematodes (Syngamus trachea, Syngamus taiga and Syngamus merulae) and one taxa, determined only to the generic level, collected from respiratory tracts of passeriform hosts from Central Europe using newly obtained sequences of 2 nuclear markers (internal transcribed spacers 1 and 2 [ITS1, ITS2]) and a fragment of mitochondrial cytochrome oxidase I [COI] gene. Our results clearly showed that S. trachea, S. taiga and S. merulae are valid, molecularly and morphologically distinct species. Moreover, molecular analysis of adult female of Syngamus sp. collected from tracheae of the European robin Erithacus rubecula clearly indicate that these comprise separate species. In the derived phylogeny, the Syngamus clade is divided into two sub-clades: one comprised Syngamus species with a characteristic, well-developed cuticular collar around the oral opening (S. trachea and S. taiga) and a second that groups taxa without or with rudimentary collar (S. merulae and currently sequenced Syngamus sp. from Erithacus rubecula). These results clearly suggest that the degree of collar development (well-developed vs. rudimentary/absent) may be an important phylogenetic feature for determining the structure of the genus Syngamus on subgeneric level. Additionally, our results support historical division of the genus Syngamus into two subgenera S. (Syngamus) and S. (Ornithogamus).

Revision of the species complex Amidostomum acutum (Lundahl, 1848) (Nematoda: Amidostomatidae) by use of molecular techniques.

The aim of the work is to confirm the species differentiation of the nematodes of the Amidostomatidae family: Amidostomoides acutum (Lundahl, 1848) Lomakin, 1991; Amidostomoides monodon (Linstow, 1882) Lomakin, 1991, and Amidostomoides petrovi (Shakhtahtinskaya, 1956) Lomakin, 1991, which still are used in the parasitological literature as synonyms of Amidostomum acutum (Lundahl, 1848). The research material consisted of nematodes isolated from gizzards of dabbling ducks from the north-west of Poland. To confirm the species differentiation, DNA from the nematodes was isolated and approximately 630bp of the 28S rRNA gene were sequenced. The obtained DNA sequences were tabulated and then phylogenetic analysis were conducted using the UPGMA method. The results of the research distinctly diversify the nematodes of the genus Amidostomoides at the DNA level, which together with morphological and ecological differences among them (hosts from different systematic groups) enables to classify them into the separate species.

Total and methylmercury in soft tissues of white-tailed eagle (Haliaeetus albicilla) and Osprey (Pandion haliaetus) collected in Poland.

Mercury (Hg) contamination in piscivorous birds, especially methylmercury (MeHg), has been drawing much attention worldwide in regard to its bioaccumulation and biomagnification in food chains. In this study on Hg in the soft tissues of white-tailed eagles (n = 22) and ospreys (n = 2) from Poland, total Hg (THg) range was 0.15-47.6 while MeHg range was 0.11-8.05 mg kg⁻¹ dry weight. In both species, median THg and MeHg concentrations were lower in the muscle and brain than in the liver and kidney. Median nephric residues were just under 3 and 5 mgTHg kg⁻¹ or 0.9 and 3.7 mgMeHg kg⁻¹ for white-tailed eagle and osprey, respectively. In Norwegian data from the 1970s and in our results, MeHg in the muscle of white-tailed eagle was ~60 % THg (%MeHg = MeHg/THg × 100), lower than in other piscivorous birds. A clear similarity in THg tissue levels was found between Polish and German populations of white-tailed eagles.

Morphometrical and ecological analysis of nematodes of the family Capillariidae (Neveu-Lemaire, 1936) in wild ducks (Anatinae) from the north-western Poland.

West Pomerania is located on the migratory route of many species of birds. Among them are many representatives of wild duck species (subfamily Anatinae), which are often the primary hosts of many helminths due to the fact of living in two different environments: terrestrial and aquatic. However, until the end of the 90s, research conducted in Poland on the helminth fauna of wild birds, including nematodes of the family Capillariidae, did not include the north-western region of the country. These first studies performed in 1999, aimed at the identification of the nematodes of wild ducks from the West Pomerania region, revealed the presence of three species belonging to family Capillariidae, i.e. Capillaria anatis (Schrank, 1790) Travassos, 1915, Eucoleus contortus (Creplin, 1839) Gagarin, 1951 and Pseudocapillaria mergi (Madsen, 1945). The purpose of the current study was to perform a comprehensive ecological analysis of C. anatis, E. contortus and P. mergi, including such factors as intensity, prevalence, relative density, index of fidelity and dominance index. The experimental material comprised 811 nematodes isolated from the gastrointestinal tracts of 953 ducks. These 9 species of ducks belong to three different tribes of the Anatinae subfamily: Anatini (Anas clypeata, A. crecca, A. platyrhynchos), Aythyini (Aythya fuligula, A. marila) and Mergini (Bucephala clangula, Clangula hyemalis, Mergus merganseri, Somateria mollissima) and diverse in terms of their biology and ecology. The morphometric and morphological analyses fail to identify any significant differences in the body structures of nematodes of the species C. anatis, E. contortus and P. mergi of the West Pomerania region in comparison with those found in other regions of Poland and Europe. The ecological analysis of the Capillariidae family in the West Pomerania region revealed that ducks of the tribe Anatini (mainly A. platyrhynchos) are the most common hosts of E. contortus species, C. anatis is most commonly found in ducks of the tribe Aythyini, and P. mergi is relatively frequent in ducks of the tribe Mergini (mainly in M. merganser).

Actitis hypoleucos (L., 1758)--new Polish host of the trematodes: Plagiorchis nanus (Rudolphi, 1802) and Leucochloridium perturbatum Pojmanska, 1969.

In July-August of 2005-2008, 47 digenean trematodes were examined from 7 specimens of the common sandpiper, Actitis hypoleucos (L., 1758). The digeneans were collected during a study on the food composition of the common sandpiper. The research was conducted near Lisewo Malborskie (near Tczew, Zulawy Wislane, Gdansk sea-coast), at a resting site on the birds' migration route. The foods ingested were extracted from live birds by draining their alimentary tracts with a nasogastric tube. Two digenean species were identified: Plagiorchis nanus Rudolphi, 1802 (Plagiorchiidae) and Leucochloridium perturbatum Pojmanska, 1969 (Leucochloridiidae). Actitis hypoleucos is the host for these new records in Poland. The P. nanus individuals isolated from A. hypoleucos differed in terms of the visible uterus and the extent of the vitellaria in the posterior part of the body.

Taxonomic structure of Digenea in wild ducks (Anatinae) from West Pomerania.

Parasitic fauna of birds connected with water environment, including digeneans, is relatively well researched in Poland. The exception, however, is West Pomerania, where those birds were not frequent objects of parasitological research until recently. The purpose of this work is to determine the taxonomic structure of the Digenea, parasitising wild ducks living in West Pomerania. The research material was 124 individuals of wild Anatinae (Anseriformes) belonging to 8 species: Anas strepera, A. crecca, A. platyrhynchos, Aythya marila, A. fuligula, Melanitta nigra, M. fusca and Mergus merganser. The ducks were obtained in the years 2001-2006 from small ponds near Szczecin, Lake Dabie, the Szczecin Lagoon and the Baltic Sea. The research showed the presence of 29 species of digeneans from 11 families: Paracoenogonimus ovatus Katsurada, 1914; Diplostomum mergi Dubois, 1932; D. parviventosum Dubois, 1932; D. phoxini (Faust, 1918); D. pusillum (Dubois, 1928); Ornithodiplostomum scardinii (Shulman in Dubinin, 1952); Echinochasmus spinulosus (Rudolphi, 1808); Echinoparyphium cinctum (Rudolphi, 1802); E. recurvatum (Linstow, 1873); Echinostoma miyagawai Ischii, 1932; E. revolutum (Fröhlich, 1802); Hypoderaeum conoideum (Bloch, 1782); Stephanoprora pseudoechinata (Olsson, 1876); Cryptocotyle concava (Creplin, 1825); C. lingua (Creplin, 1825); Leucochloridiomorpha lutea (von Baer, 1826); Catatropis verrucosa (Fröhlich, 1789); Notocotylus attenuatus (Rudolphi, 1809); Paramonostomum alveatum (Mehlis, 1846); Metorchis xanthostomus (Creplin, 1846); Prosthogonimus ovatus (Rudolphi, 1803); P. rarus Braun, 1901; Psilochasmus oxyurus (Creplin, 1825); Psilostomum brevicolle (Creplin, 1829); Psilotrema simillimum (Mühling, 1898); Bilharziella polonica (Kowalewski, 1895); Apatemon gracilis (Rudolphi, 1819); Australapatemon minor (Yamaguti, 1933); Cotylurus cornutus (Rudolphi, 1808).

[Digenea in Melanitta fusca and M. nigra (Mergini, Anseriformes) from the Baltic Sea]. / Digenea Melanitta fusca i M. nigra (Mergini, Anseriformes) z Morza Baltyckiego.

Ten individuals of Melanitta fusca and M. nigra (Mergini, Anseriformes) each, wintering at the Polish Baltic coast, were examined for the presence of parasites. M. fusca yielded a total of 197 helminths, including 20 digeneans and 177 nematodes. The M. nigra individuals examined were found to support 923 helminths, including 62 digeneans, 860 nematodes, and a single cestode. M. fusca were hosts to the digeneans: Cryptocotyle concava, Notocotylus attenuatus and Psilostomum brevicolle. Digenea found in M. nigra represented: C. concava and Paramonostomum alveatum. The prevalence of P. brevicolle infection (60%) was higher than that of other digeneans; the maximum infection intensity was 40 C. concava individuals in a single M. nigra.

[Enteric helminths of the mallard Anas platyrhynchos L., 1758 in the north-western part of Poland]. / Helmintofauna przewodu pokarmowego krzyzówki Anas platyrhynchos L., 1758 pólnocno-zachodniej Polski.

Although the mallard, Anas platyrhynchos, is the most common wild duck in Poland, as well as in the entire Palearctic, it is extremely rarely studied by comprehensive parasitological surveys. The aim of this study was to present a synthesis on the species composition of enteric helminths of the mallard in north-western Poland. The study was carried out in 1999-2006 and involved parasitic worms isolated from the alimentary tracts of 187 mallards (Anseriformes: Anatidae). Following isolation, the parasites were preserved in 70% ethylene and stained (flatworms) or viewed in transient light (nematodes and acanthocephalans). Taxonomic identity of the worms was determined using taxonomic keys and numerous original papers. The studies have revealed that the parasitic community of this host in the north-west part of Poland is relatively complex, composed of 51 species of helminths of four systematic groups: 16 digenean species, 23 tapeworms, 9 nematodes, and 3 acanthocephalans. The material also revealed five new to Polish fauna parasitic species: one trematode (Echinostoma miyagawai) and four tapeworms (Microsomacanthus baeri, M. pachycephala, Monotestilepis tadornae, and Sobolevicanthus aculeostileticus). On the other hand, for another 11 species (Prosthogonimus ovatus, Psilotrema simillimum, Australapatemon minor, Leucochloridiomorpha lutea, Psilostomum brevicolle, Echinocotyle rosseteri, Fimbriarioides sp., Retinometra giranensis, Anisakinae gen. sp., Pseudocapillaria mergi i Polymorphus magnus) the mallard was found to be a new host.